Current Transformers

Current transformers (CT) are devices that are used to transform the current from a high current into a lower current so that the power can then be measured and controlled. The transformers consist of a core, a primary and a secondary winding. When an alternating current flows through the primary winding, a magnetic flux is created which then induces an alternating current in the secondary winding. This alternating current is proportional to the current in its primary. Current transformers are also known as a "step-down transformers". Once the current has been reduced it can be safely monitored and measured using an ammeter.


Current transformers can perform circuit control and perform roles for safety protection and current limiting.


Current transformers are found in:


  • Generating stations,

  • Electrical substations

  • Commercial electric power distribution.

Types of Current Transformers


Toroidal Current Transformer - These transformers are shaped like a doughnut they do not contain a primary winding. Instead, the line that carries the current flowing in the network is threaded through a window or hole in the toroidal transformer. Toroidal transformers offer high efficiency with minimal excess noise and little excess leakage inductance.


Wound Current Transformer - The transformers primary winding is physically connected in series with the conductor that carries the measured current flowing in the circuit. The magnitude of the secondary current is dependent on the turns ratio of the transformer.


Bar-type Current Transformer – This type of current transformer uses the actual cable or bus-bar of the main circuit as the primary winding, which is equivalent to a single turn. They are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device.


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Description Price Current Ratio Inner Diameter Transformer Type Overall Height Overall Width Input Current Overall Depth Output Current Minimum Temperature Maximum Temperature Dimensions For Use With Mounting Type Series
RS Stock No. 171-8808
BrandRS PRO
MYR159.49
Each
units
1500:1 61 x 51mm - 110mm 86mm - 45mm - - - 86 x 45 x 110 mm - - -
RS Stock No. 124-3902
BrandRS PRO
MYR16.28
Each
units
- - - - - 50A - - -40°C +85°C 23.8 x 11.12 x 23.8 mm - PCB Mount -
RS Stock No. 124-3900
BrandRS PRO
MYR22.08
Each
units
- - - - - 10A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0201
BrandRS PRO
MYR14.468
Each (In a Box of 114)
units
- - - - - 60 → 200A - - -55°C +130°C 38.1 x 15.9 x 38.1 mm - PCB Mount -
RS Stock No. 171-8783
BrandRS PRO
MYR90.65
Each
units
150:5 30 x 11mm Clip Fit 78mm 62mm 150A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm - Surface Mount -
RS Stock No. 171-8755
BrandRS PRO
MYR60.98
Each
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100:5 21 x 10mm Clip Fit 65mm 45mm 100A 40mm 5 A -5°C +55°C 45 x 40 x 65 mm - Surface Mount -
RS Stock No. 171-8815
BrandRS PRO
MYR166.76
Each
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1500:5 80 x 12mm Clip Fit 126mm 104mm 1.5kA 45mm 5 A -5°C +55°C 104 x 45 x 126 mm - Surface Mount -
RS Stock No. 173-0200
BrandRS PRO
MYR101.482
Each (In a Box of 133)
units
- - - - - 50 → 125A - - -55°C +130°C 34.9 x 14.3 x 34.9 mm - PCB Mount -
RS Stock No. 171-8829
BrandRS PRO
MYR124.56
Each
units
250:5 35mm Base Mounted 87.5mm 105mm 250A 38mm 5 A - - 105 x 38 x 87.5 mm MCCB Surface Mount -
RS Stock No. 171-8841
BrandRS PRO
MYR297.96
Each
units
1250:5 101 x 56mm Clip Fit 170mm 130mm 1.25kA 60mm 5 A -5°C +55°C 130 x 60 x 170 mm - Surface Mount -
RS Stock No. 171-8825
BrandRS PRO
MYR124.56
Each
units
125:5 35mm Base Mounted 87.5mm 105mm 125A 38mm 5 A - - 105 x 38 x 87.5 mm MCCB Surface Mount -
RS Stock No. 171-8772
BrandRS PRO
MYR79.04
Each
units
250:1 30 x 10mm - 70mm 50mm - 30mm - - - 50 x 30 x 70 mm - - -
RS Stock No. 171-8757
BrandRS PRO
MYR86.98
Each
units
- - - - - - - - - - - - - -
RS Stock No. 171-8773
BrandRS PRO
MYR52.90
Each
units
250:5 30 x 10mm Clip Fit 70mm 50mm 250A 31mm 5 A -5°C +55°C 50 x 31 x 70 mm - Surface Mount -
RS Stock No. 173-0216
BrandRS PRO
MYR17.848
Each (In a Box of 351)
units
- - - - - 7.5A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3897
BrandRS PRO
MYR20.94
Each
units
- - - - - 50A - - -40°C +85°C 19 x 11.5 x 21.5 mm - PCB Mount -
RS Stock No. 173-0219
BrandRS PRO
MYR51.728
Each (In a Box of 18)
units
- - - - - 200 → 500A - - -55°C +130°C 55.6 x 20.6 x 55.6 mm - PCB Mount -
RS Stock No. 171-8791
BrandRS PRO
MYR73.44
Each
units
400:5 40 x 11mm Clip Fit 78mm 62mm 400A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm - Surface Mount -
RS Stock No. 171-8857
BrandRS PRO
MYR92.92
Each
units
15:5 62 x 40mm Clip Fit 78mm 62mm 15A 40mm 5 A -5°C +55°C 62 x 40 x 78 mm - Surface Mount -
RS Stock No. 173-0199
BrandRS PRO
MYR15.065
Each (In a Box of 133)
units
- - - - - 40 → 125A - - -55°C +130°C 34.9 x 14.3 x 34.9 mm - PCB Mount -
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